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On October 28th, after completing the related work in the technical area at Wenchang launch site in Hainan, China’s largest new generation launch vehicle Long March 5, which carried out its mission for the first time, was successfully transported vertically to the launch area, and it is planned to launch it at the beginning of November.
The Long March 5 carrier rocket developed by China Aerospace Science and Technology Corporation is a new generation of large-scale cryogenic liquid-bound carrier rocket in China. Its geosynchronous transfer orbit carrying capacity is 13 tons, and its near-earth orbit carrying capacity is 25 tons, which can be compared with large foreign rockets currently in service. Its main features are great strength, strong body, low cost, no pollution and more reliability … …
Why build the Long March 5?
At present, China’s conventional "Long March" series of launch vehicles have made remarkable achievements, and their reliability has reached the advanced level in the world, which can basically meet the transportation needs of China entering space.
However, since the 21st century, the world’s major space powers have launched a new generation of large-scale launch vehicles, such as Cosmos 5, Delta 4 and Ariane 5 in Europe. They not only have large thrust and the carrying capacity in low-earth orbit reaches 20 tons, but also use cheap, non-toxic and pollution-free low-temperature propellant.
Compared with similar foreign rockets, China’s mature rockets in active service still have a certain gap. For example, the carrying capacity is small; Most of them also use high-cost, toxic and polluting propellants.
In order to meet the needs of China’s major space engineering tasks in the future, especially the needs of space development in the next 20-30 years, and catch up with the advanced level of foreign new large-thrust launch vehicles, in October 2006, China began to develop the Long March 5 new generation large-scale launch vehicle. It has a series of new characteristics: large diameter, large thrust, few stages, serialization, low cost, high reliability, easy operation, no pollution, wide application and so on, and its carrying capacity is the same as that of foreign mainstream launch vehicles.
The Long March 5 all-arrow adopted 247 core key new technologies, and the proportion of new technologies reached almost 100%. In the international development of new rockets, including satellites and spacecraft, the proportion of adopting new technologies generally does not exceed 30%. In the past, the "Long March" rocket used tens of thousands of parts at most, while the Long March 5 rocket used hundreds of thousands of parts, and its design quantity was more than 3.5 times that of the previous "Long March" rocket.
According to the plan, in 2017, China will use the Long March 5 to launch the Chang ‘e-5 lunar sampling returner, in 2018, it will start to launch the 20-ton space station module one after another, and in 2020, it will launch the first Mars probe in China … …
Big physique, great strength and great difficulty
As a new generation of launch vehicle with the largest carrying capacity in China, Long March 5 integrates many latest space technologies. For example, the 5-meter-diameter arrow structure is adopted for the first time, and the non-toxic and pollution-free combined take-off scheme of liquid hydrogen/liquid oxygen and liquid oxygen/kerosene engine is used for the first time. Because of its large size, great strength and great difficulty, Long March 5 is also called "Big Rocket" for short, and it is the first heavy rocket in Asia at present.
The Long March 5 is equipped with three kinds of 12 new high-thrust cryogenic engines and sufficient fuel, so the power is very strong. Its take-off thrust exceeds 1,000 tons, which makes China’s ability to enter space more than 2.5 times, crossing the "threshold" of international large-scale launch vehicles with a low-orbit carrying capacity of 20 tons and a high-orbit carrying capacity of 10 tons, and some technical indicators still exceed those of the world’s major large rockets such as the United States and Europe.
Its core has a diameter of 5 meters and is bundled with four boosters with a diameter of 3.35 meters. Previously, the diameter of China’s rocket core was 3.35 meters, and the diameter of booster was 2.25 meters. Because the Long March 5 is thick, everyone affectionately calls it "Fat Five". Long March 5 was designed as a "big body" in order to accommodate more propellant and generate more thrust. This can also reduce the number of stages of the rocket, thus reducing the separation times of the rocket and improving the reliability and control ability of the rocket. This is the development trend of contemporary new high-thrust rockets.
In addition, the core engine of Long March 5 uses liquid hydrogen/liquid oxygen fuel, while the booster uses liquid oxygen/kerosene fuel. It is the first time in China that this combined take-off scheme uses two kinds of non-toxic and pollution-free low-temperature fuel engines at the same time. The reason why this complex combined takeoff scheme is adopted is that the working time of the first and second cores is long, so it is suitable to adopt the liquid hydrogen/liquid oxygen power system with high specific impulse; The working time of the booster is relatively short, so it is suitable to use the liquid oxygen/kerosene power system with large thrust and high propellant density to increase the specific impulse of the engine. By adopting this scheme, the rocket scale is the smallest and the number of engines used is the least, thus effectively improving the carrying capacity and efficiency.
It is the first time in the development history of China’s launch vehicle that all its core stages use low-temperature propellant. Because the temperature of liquid hydrogen is -253℃ and liquid oxygen is -183℃, the interior of Long March 5 is extremely low temperature far below the freezing point, which is a veritable "ice arrow". Because its combustion produces water, the rocket is non-toxic and pollution-free, which also marks a new step in the reliability, safety, adaptability and environmental friendliness of the launch vehicle in China.
Change "carrying the burden" to "carrying the sedan chair"
The reason why Long March 5 achieved the international advancement of various performance indexes was that it broke through 12 major key technologies in an all-round way, including: structural design, manufacturing and testing technologies for large-scale arrow bodies with a diameter of 5 meters; 120-ton liquid oxygen/kerosene engine technology; 50-ton liquid oxygen/liquid hydrogen engine technology; 9-ton thrust liquid hydrogen/liquid oxygen engine technology; Rocking suppression technology of large cryogenic rocket: Low-temperature pressurized conveying system with circulating pre-cooling technology and new valve technology; Booster engine swing and front fulcrum force transfer attitude control technology of large liquid launch vehicle, etc. These are the major core key technologies encountered for the first time in the history of launch vehicle development in China, and they are also difficult problems in rocket development in the world.
In addition, it has broken through many other technologies, for example, its vertical transshipment technology is extraordinary. Because the Long March 5 rocket is about 57 meters long, equivalent to 20 stories high, and weighs more than 600 tons, it was "walked" on the 2800-meter seamless rail for about 2 hours with a movable launching platform half the size of a football field, that is, its vertical transfer speed did not exceed 30 meters per minute. Along the way, the mobile launch platform not only carries the Long March 5 rocket, but also supplies gas and power for the rocket. In this way, the connection between the rocket and the ground can be kept unchanged during the transition of the rocket, thus reducing the work in the launch area and shortening the launch process.
In the transition method, it is also very different from the active rocket. Other rockets are "shouldering the burden", and the Long March 5 rocket is "lifting the sedan chair" to "walk" more stably. What does this mean? In the vertical transition of the rocket, there are four support arms at the "foot" of the active rocket core level, which are used to let the rocket "stand" on the "car" steadily. The rocket booster is "carried" and "walked" by the core level, so it is called "carrying the burden". The Long March 5 rocket has 12 support arms during the transition, but they are evenly distributed at the "feet" of the four boosters, so the four boosters "lift" the core level, so it is very similar to "lift the sedan chair". Its transition can reach 8-9 winds, and there is no need for any wind-proof and load-shedding device in the middle. The successful completion of vertical transshipment marks that the first flight mission of the Long March 5 carrier rocket officially entered the launch stage.
Can be combined like building blocks.
On the basis of extensive and in-depth analysis and research on the latest launch vehicle technology and future development trend in the world, China’s Long March 5 series launch vehicle adopted the general idea of "one series, two engines and three modules" and implemented the design principle of "generalization, combination and serialization". Different combinations of the three modules and the core stage can form six configurations of a new generation of large-scale launch vehicles with a core stage diameter of 5 meters, and a new generation of medium-sized and small-sized launch vehicles can be derived from the new generation of large-scale launch vehicles. Using modular design idea can realize technology sharing, improve reliability, save cost and shorten development cycle.
The basic model of Long March 5 is a two-stage semi-rocket with booster, with a total length of 57 meters. Its take-off mass is 878 tons, take-off thrust is 1078 tons, and the carrying capacity of geosynchronous transfer orbit is 14 tons, which is used to launch the Chang ‘e-5 lunar sampling returner.
The Long March 5 B rocket dropped the second stage on the basis of Long March 5, which was used to launch the cabin of China’s 20-ton space station. This one-and-a-half-stage rocket with booster has a total length of 53.7 meters, a take-off weight of 837.5 tons, a take-off thrust of 1,078 tons, and a low-earth orbit carrying capacity of more than 22 tons.
Long March 5/Expedition 2 is a three-stage rocket with booster. Based on the basic model of Long March 5, it added the upper stage of Expedition 2 as the third stage. It mainly performs launching tasks such as large-scale geostationary orbit and circular orbit in Beidou navigation. The Long March 5, which was first launched this time, is this model.
Extended reading
Why launch near the coast?
High-thrust rocket is the first prerequisite for completing major aerospace engineering tasks such as building a manned space station and deep space exploration, and it is also a necessary condition for human beings to return to the moon and land on Mars. However, the diameter of large thrust rockets is very large. For the three launch sites in China, transporting large rockets has always been a difficult problem, because when the diameter exceeds 3.5 meters, the trains transporting rockets cannot pass through culverts.
The Long March 5 series carrier rockets have a diameter of 5 meters, so they cannot be transported to three inland launch sites in China by train. Wenchang Satellite Launch Center is located near the coast of Hainan, and has a good port where ships carrying large rockets can be parked. This is the most important reason for launching the Long March 5 carrier rocket in Wenchang, Hainan. It adopts road-sea-road transportation mode, and the Long March 5 carrier rocket is transported from Tianjin to Hainan by two special transport ships. China’s future heavy-duty launch vehicle is about 10 meters in diameter, so it is likely to be launched in Wenchang, Hainan.